Electroplating of high tungsten content Ni/W alloys

Induced codeposition of tungsten with nickel from aqueous solutions of sodium tungstate was studied. Ammonia is commonly added to such plating baths to adjust the pH, but its role as a ligand for nickel complexes is usually ignored. Removing ammonia helped to increase the tungsten content of the alloy to 50 atom % (76 wt %). First indications for the formation of an amorphous Ni/W alloy at intermediate concentrations of tungsten (20-40 atom %) were observed. It is shown that the reported effect of temperature on the composition of the alloy is due to the removal of ammonia from solution. In its absence, the tungsten content of the alloy plated from a given solution is essentially independent of temperature. (C) 2000 The Electrochemical Society. S1099-0062(00)07-098-X. All rights reserved.